ModelSpaceRotation of bones in skeleton. How to rotate bones around same axis?


I am working on a scientific application which should visualize hand movements in 3D with JME. I measure the hand movements with some inertial measurement sensors, which give me a relative rotation to an arbitrary start quaternion.

I have created a hand with skeleton in Blender and could successfully import it with ogreimporter. I am also able to manipulate single bones of my hand skeleton.

I am using following function, which is based on a similar one in RagdollControlUtils



  • Updates a bone position and rotation.

  • @param bone
  •        the bone<br />
  • @param pos
  •        the position<br />
  • @param rot
  •        the rotation<br />


public static void setTransform(Bone bone, Vector3f pos, Quaternion rot,

boolean restoreBoneControl) {

// we ensure that we have the control


// we set te user transforms of the bone

bone.setUserTransformsWorld(pos, rot);

for (Bone childBone : bone.getChildren()) {

Transform t = childBone.getCombinedTransform(pos, rot);

setTransform(childBone, t.getTranslation(), t.getRotation(),



// we give back the control to the keyframed animation

if (restoreBoneControl) {





For mapping my sensors to bones I need to initialize my sensor fusion algorithm with start quaternions. So I had the idea of taking the ModelSpaceRotation of my fresh loaded model and update these orientations afterwards with the relative movements of my sensors. This is working, but I need to align the axis of my sensors with the axis of the bones for getting a proper rotation.

On working on that I checked out the initial quaternions of my hand model, but I do not understand why they seems to have different local coordinate systems. All bones are obviously in parallel and pointing upwards on the global y axis, but the root bone has quaternion (w,x,y,z) of (1,0,0,0) and all finger bones have a quaternion of (0,0,1,0) or (0,0,-1,0). I never have rotated these bones in blender, they are strait extruded in one axis from the root bone.

Here is a image of my hand

It is necessary for me to align all quaternions to one coordinate system to get a proper matching with my sensors.

Can some explain or help on this problem? Or could tell me how I can align all coordinate systems to one orientation?

Look at the source of the KinematicRagDollControl, it also moves the bones according to absolute world positions of the physics objects. Also make sure you understand the implications of parent/child relations (scale, rotation and location work together, you cannot just work with rotation).

I have solved the problem. The local coordinate systems of my bones in blender were different, don’t know why, because I never rotated them…